Methods of heating an article in a microwave oven

ABSTRACT

Methods of heating an article using microwave absorptive material, microwave absorptive combustible material, microwave nonabsorptive material, heat insulating material and/or heat conducting material are described. A process and an implement for converting microwave energy into heat energy which includes a body having a plurality of resistive particles therein. Upon subjecting the particles to microwave irradiation, a plurality of electric arcs are generated throughout the particles, thereby resulting in the microwave energy being converted into heat energy, and the electric arcs serving as a load for the microwave irradiation source. The implement is particularly useful with microwave ovens.

I United States Patent 1191 1111 3,777,099 Levinson 1 Dec. 4, 1973 [54]METHODS OF HEATING AN ARTICLE IN A 3,182,164 5/1965 lronfield 219 1055MICROWAVE OVEN FOREIGN PATENTS 0R APPLICATIONS Inventor: MelvinLevinson, 1 Meinzer 1,049,019 1/1959 Germany 219/1055 Avenel, NJ. 07001s p 2 Prirrmry Examir ler l. Truhe l N 293 006 Assistant Exammer-J-lughD. Jaeger [21] App 0.:

Related US. Application Data RACT [60] Division of Ser, No. 704,389,Feb. 9, 1968, Pat. No. Me h f heating an ar icle using microwave ab-3,701,872, which is a continuation-in-part of Ser. No. sorptivematerial, microwave absorptive combustible u y 1965, abandonfid, and amaterial, microwave nonabsorptive material, heat incommuauon-m'part of$91 483,144 27, sulating material and/or heat conducting material are1965, abandoned. described 52 us. c1. 219/1055 Pmcess and f imp'emem 511111. C1. "05b 9/06 energy Ff mcludes, 581 Field of Search 219/1041,10.51, body a Plural'ty PamclesI them 219/10 55 1065 Upon sub ectlng theparticles to microwave irradiation, a plurality of electric arcs aregenerated 961 m1c wav energy e1 g c e 1 e e gy, UNITED STATES PATENTSand the electric arcs serving as a load for the 2,830,162 4/1958 Copsmet a1 219/1055 microwave irradiation Source The implement is wi ex fparticularly useful with microwave ovens. 1 e 3,420,923 1/ 1969 Ashworthet al..' 219/ 10.55 UX 13 Claims, 8 Drawing Figures j \\\\Lk\ METHODS OFHEATING AN ARTICLE IN A MICROWAVE OVEN CROSS-REFERENCES TO RELATEDAPPLICATIONS This application is a division of application Ser. No.

704,389 filed Feb. 9, 1968, now Pat. No. 3,701,872

which in turn is a continuation-in-part of Ser. No. 470,809, filed July9, 1965 now abandoned and a continuation-in-part of Ser. No. 483,144filed Aug. 27, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an implement whichin response to microwave irradiation is capable of processing and/orcooking a load. More particularly, this invention relates to animplement capable of converting microwave energy into heat energy whichmay thence be directed to an object to be processed.

Microwave ovens are extremely useful as cooking ovens; however, withconventional type microwave ovens, the searing, browning and crusting offoods constitutes a problem and requires either additional gas orelectric heating elements in the microwave oven or the use of anexternally located heating apparatus not related to the microwave oven.It is apparent that the heretofore methods employed for searing,browning and crusting are cumbersome, costly, time-consuming andgenerally unappealing to the users thereof.

Accordingly, one of the objects of this invention is a processforconverting microwave energy into heat energy.

Another object of this invention is to provide an implement directlyassociated with microwave ovens so as to lend versatility to the cookingof foodstuffs. Advantageously, foodstuffs can be fried, roasted, grilledand baked with the desired crusting surface thereon.

Another object of this invention is to provide a microwave oven capableof cooking a foodstuff with a desired crusting surface thereon.

Still another object of this invention is to provide an implement for amicrowave oven which, per se, is capable of acting as a dummy load for amicrowave emitting source.

SUMMARY OF THE INVENTION According to the objects of'this invention, animplement, preferably taking the form of a cooling utensil or mocrowaveoven shelf, is provided with a plurality of wave source BRIEFDESCRIPTION OF THE DRAWINGS Otherobjects and a fuller understanding ofthe invention may be had by referring to the drawings wherein:

FIG. 1 is a cross-sectional view of the implement taking the form of acooking utensil;

FIG. 2 is a cross-sectional view of another embodiment of the implementtaking the form of a hot cube;

FIG. 3 is a cross-sectional side view of a microwave oven havingincorporated'therein another embodiment of the implement in the form ofa shelf;

FIG. 4 is a view taken along line 4 4 of FIG. 3;

FIG. 5 is a cross-sectional side view of a microwave oven havingincorporated therein another embodiment of the implement in the form ofa shelf;

FIG. 6 is a cross-sectional front view of a microwave oven havingincorporated therein another embodiment of the implement in the form oftwo shelves;

FIG. 7 is a cross-sectional side view of a microwave oven havingincorporated therein another embodiment of the implement in the form ofan electrical charcoal grill; and

FIG. 8 is a partial cross-sectional, plan view of another embodiment ofthe implement in the form of a grill-shelf.

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings,it will be apparent that the inventive implement may be constructed andutilized in various embodiments. According to one embodiment, as seen inFIG. 1, an implement I, is in the form of a cooking utensil and includesa body 10 which is permeable to microwave irradiation and preferablemade of glass-ceramic type material, such as Pyroceram (manufactured byCorning Glass Works) or Cer- Vit (manufactured by Owens-Illinois).Located within body 10 is a bed or layer of particles 11 of a resistivematerial supported on an insulating medium 12 which may be of a materialsuch as GR25 (manufactured by General Refractories Company). A good heatconducting element 13, in the form of a plate, copper strips, rods,etc., is preferably located in contact with the particle bed 11. Theheat conducting element 13, as illustrated in FIG. 1, preferably is aflat copper plate provided with openings 15-15 therethrough to permitthe free random passage of microwave waves to and through the particles.In the event it is desired to utilize implement I, as a dummy load, perse, for a microwave emitting source, the heat conducting element 13 maybe provided with a plurality of fins 16-16, as seen in phantom, whichextend from the implement structure to cause a free release of heattherefrom. A top processing surface 17, made of a material similar tobody 10, is in contact with heat conducting element 13, and is attachedto the body at 18 by a suitable adhesive.

It has been found that the resistive particles 11 are, in actuality, aplurality of electrodes which support a plurality of spark gaps todischarge microwave energy therebetween. There are innumerable solidmetals which will support an electric gap or arc. For example, theparticles may be of a ferrite material having a high resistance toproduce a relatively cool spark, when it is desired to use the implementas a household cooking utensil. On the other hand, a carbon materialwhich possesses low resistance and produces a relatively hot spark maybe utilized, when the implement is desired to be used in a refractoryprocess for vapourizing metals. With the latter, ultra high heattemperatures may be obtained when considering carbons melting point(approximately 6,500F).

With respect to the heat insulation 12, it is of a material, such asdescribed above,'which is permeable to microwave energy and not lossy orself-heating when exposed to microwave energy. The heat insulation has adual purpose; firstly, to direct the heat to the workload and, secondly,when the implement is used as a cooking utensil, to protect the cook andconfine the heat generated by the arcing from a table subsequentlyreceiving the implement.

Regarding the body or casing 10, it should be of a material, such asstated above, which is permeable to microwaves and not lossy orself-heating when exposed to microwave energy. The body is used toprotectively contain the fragile heat insulating material and the looseplie or layer of resistive particles. Generally, the body or casing isconstructed by sealing two portions together, one portion holding theparticles and the other enclosing the particles and serving as a cookingsurface.

With respect to heat conducting element 13, it is of a material, such asstated above, which is capable of equalizing the heat generated. Theheat conducting material may be of the same material as the resistiveparticles or of a material complementary thereto, such as copper havinga low resistance and ferrite having a high resistance. It is apparent,however, that materials having a low melting point, such as aluminum,may not be used with materials having a high melting point, such ascarbon, when temperatures in excess of the low melting point materialare required.

In operation, the implement is located in a suitable microwave cavity(not shown) and exposed to microwave irradiation, the microwavescontacting the particles 11. In response thereto, a plurality ofelectric arcs are generated throughout and between the particles 11 andthe heat conducting element 13. Within a relatively short time, theparticle bed appears as a glowing bed of coal emitting a high degree ofheat in excess of 1,000F. The amount of heat generated is dependent uponthe amount and size of the resistive particles, the quantity of thereleased microwave energy and the time. The microwave arcing tends toterminate the released microwave power and, as a result, precludes asufficient degree of reflection of microwave power back to the source,thereby preventing any damage thereto. It is apparent that the higherthe output power of the microwave generator, the more resistiveparticles required to properly terminate it.

FIG. 2 is illustrative of another embodiment of the implement, referredto as I which takes the form of a hot cube. Implement I includes anouter coating of a suitable microwave permeable material, such asglass-ceramic, epoxy and, in this instance, preferably cardboard. Asimple heat insulating material 12b, such as sand concrete or castablerefractory material, is located within the outer coating 10b andcompletely envelops a bed of resistive particles 1 1b of a material suchas a relatively inexpensive high-grade iron ore.

After exposure to microwave irradiation, the heat stored within the hotcube releases and can be used advantageously as a warmer for articles oranimals. For example, the hot cube may be easily inserted intoinsulating containers (not shown) whereupon the stored heat releasesfrom the hot cube to heat or cook a foodstuff in proximity thereto.Similarly, the hot cube may serve as a body warmer for people. Theduration of the released heat is commensurate with the size and type ofinsulation coupled with the quantity of microwave irradiation of theparticle bed. Significantly, in view of this low cost of fabricating ahot cube", such may be marketed as a disposable item.

While the implement has heretofore been discussed with respect to itsuse as a portable type article; namely a cooking utensil, hot cube, bodywarmer and the like,

the implement also may take the form of a shelf or shelves in aimcrowave oven. As seen in FIG. 3 and 4, there is illustrated amicrowave oven 25 which is provided with a conventional microwave source26, such as a generator or magnetron, for supplying microwave energyinto cavity 27 through waveguide 28. An implement, generally referred toas I takes the form of a shelf and includes a supporting element 30 forholding a ceramic type body 10c. Located within the body is aninsulating medium 12c having positioned thereon a plurality of resitiveparticles 110. A heat conducting element 13c, having an openingextending therethrough, is disposed in contact with the particles andthe top portion of body 100, the top portion 17c being capable ofreceiving a foodstuff F thereon through closure 31.

The supporting element 30 is pivotally adjustable at pivot 32 locatednear the rearmost portion of the oven and is provided with cooperatingadjustable pins 33 near the foremost portion of the oven for insertioninto various openings 34-34 for locking the implement-shelf 1;, in adesired angular position. As a result of the angular position of theimplement-shelf I any by-products of cooking, such as rendered fat,which results from the operation of the microwaves and implement aspreviously described, will pass by gravity through opening 35 of adownwardly converging bottom 36 into a portable container 37 forsubsequent use or disposal.

As seen in FIG. 5, there is illustrated another embodiment of theinvention wherein the implement, referred to as I takes the form of anupper shelf in an oven 25d. The oven is similar to the oven in FIGS. 3and 4 with the exception that the implement-shelf I is in an invertedposition. As seen in FIG. 5, the implement-shelf l rests on supportingelements 33d-33d and includes a bottom ceramic or quartz radiant panel10d. An insulating medium 12d is provided on the top side of the shelfand houses a bed of resistive particles 11d therein. The insulatingmedium 12d herein takes on the added function of dividing the ovencavity so as to create a hot lower cavity and a relatively cooler uppercavity. A conventional bottom shelf 35, premeable to microwave energy,is provided on supporting elements 36-36 for holding a utensil 37 with afoodstuff, f, thereon.

The operation is similar to that previously described with respect tothe oven in FIGS. 3 and 4. Typically, the microwave generator is turnedon and the implement shelf i is preheated until the radiant panel 10dbecomes hot, whereupon a foodstuff is placed under the radiant shelf.The foodstuff is cooked from both the microwave irradiation and theinfra red radiation. Additionally, if an extra heavy, relatively darkercrust is desired on the foodstuff, e.g. one which is cooked rare, theimplement-shelf 1;, may be modified by conventional means to be movable,thus enabling the implement-shelf to be positioned into intimate contactwith the foodstuff for a suitable period of time.

FIG. 6 discloses still another embodiment of the invention wherein theimplement, referred to as 1 -1 takes the form of a pair ofimplement-shelves which may either be fixed or mobable with respect toeach other. As seen therein, lower implement-shelf I rests on adjustablesupporting elements 332 and is provided with a bottom portion 12c, a bedof particles lle and a top insulating portion 10:: which cooperates withthe bottom portion to encase the particle bed. Similarly, upperimplement-shelf I rests on adjustable supporting elements 33e and isprovided with a top portion s, a bed of resistive particles lie, and abottom insulating portion 12e which encases the particle bed incooperation with the top portion. Optionally, a rotating spit 40 drivenby a chain 41 connected to a motor (not shown) may be employed.

The implement shelves l -l may be moved as desired, i.e., towards eachother, either separately or together or into contacting or nearlycontacting relationships with the foodstuff F to obtain additionalcrusting on opposite sides thereof, in a similar manner as discussedwith respect to FIG. 5. It should be noted that while manual means areillustated to show relative movement of the shelves, suitableconventional mechanical or electromechanical means may be employedwithout departing from the invention.

FIG. 7 discloses still another embodiment of the invention and in itssimplest structure, wherein the implement, referred to as 1 takes theform of a microwave charcoal grill. Implement I is comprised of a body10f having a plurality of resistive particles 11f therein. Typically, aceramic or metallic grill 43, illustrated with a foodstuff F thereon,may either be placed on or above the particle bed 11f.

A microwave irradiation source 26f is located in the bottom portion ofthe oven 25f and, when energized, emits waves through waveguide 27f. Thetop portion of the oven is provided with a grid 45 having relativelysmall openings 46-46. The openings 46-46 are sufficiently small so as toconfine microwave energy therein, yet sufficiently large to permit thepassage of air therethrough for disposal of by-products of combustion.Upon energization of the microwave source 26f, conversion of themicrowave energy into heat energy results in a similar manner ashereinbefore described. It should be noted that if the resistiveparticles llf are of a material, such as carbon, which will ignite whenheated in the presence of air, the burning carbon, buring fat and themicrowave energy will swiftly barbeque the foodstuff F.

FIG. 8 discloses still another inventive implement wherein theimplement, referred to as I is capable of taking the form of agrill-shelf which may be used as a substitute for implemnt shelf lillustrated in FIG. 3. Here a ceramic frame 50 holds hollow ceramic orquartz tubes 51 filled with a plurality of resistive particles 52.

In operation, grill shelf 1,, is positioned in a microwave oven andpreheated whereupon a foodstuff, such as a frozen steak, is placedthereon. With the aid of the energy from the microwave source, the steakis defrosted and cooked with a resultant grill pattern thereon which issimilar to that obtained in prior art steak grilling, the gravy juicebeing collected in container 37. Additionally, the ceramic frameimplement I remains cool and can be easily transported with the steakthereon to a receiving table.

it is to be understood that the above described arrangements of thevarious implements are illustrative of the application of the principalof the invention, each implement employing, at least, a plurality ofresistive particles therein capable of receiving and convertingmicrowave energy into heat energy. Numerous other arrangements may bedevised by those skilled in the art present invention is to be limitedonly by the spirit and scope of the appended claims.

I claim:

1. A method of heating an article in an oven chamber receptive tomicrowave energy comprising:

locating within said chamber a microwave absorptive member,

locating a heat conducting member in (a preselected relationship)contact with said absorptive member and between said microwaveabsorptive member and said article, and

exposing said microwave absorptive member to microwave energy until itabsorbs and so converts said microwave energy (into) to heat energy andsaid heat conducting member conducts said generated heat energy to saidarticle.

2. A method of barbecuing a foodstuff in an oven chamber receptive tomicrowave energy which comprises:

locating a microwave absorptive member within said oven chamber,

locating said foodstuff where said microwave absorptive member, whenheated, will be in position to heat said foodstuff and where at least aportion of any conbustible heat rendered by-products of said foodstuffwill contact said mocrowave absorptive member,

exposing said microwave absorptive member to microwave energy until itabsorbs and so converts said microwave energy to heat energy to atemperature at least high enough to heat render combustible by-productsfrom said article and high enough to kindle said combustible heatrendered byproducts, and

additionally heating said foodstuff by the heat of rapid combustion ofsaid kindled combustible heat rendered by-products.

3. A method of heating an article in an oven chamber receptive tomicrowave energy which comprises:

locating a microwave absorptive, combustible material in said ovenchamber,

exposing said microwave absorptive, combustible material to microwaveenergy until it absorbs and so converts said microwave energy to heatenergy and heats to its ignition temperature and is set on fire, and

locating said article in a predetermine position where said article willbe heated by the dual heating of both the heat of combustion of saidburning microwave absorptive, combustible material and, as it isreleased from said material, heat converted from said microwave exposureof said microwave absorptive, combustible material by said exposure ofsaid material to microwave energy.

4. In a method, according to claim 3, the added step of:

locating a heat conductive member in contact with said article andbetween said article and said burning microwave absorptive, combustiblematerial whereat to collect and conduct to said article heat energyreleased by said burning microwave absorptive, combustible material onsaid exposure to microwave energy.

5. A method of heating an implement and storing said heat within saidimplement while in an oven chamber receptive to microwave energy forsubsequent use of said heated implement at a location external said ovenchamber which comprises:

locating said implement, said implement comprising a microwaveabsorptive member located within a microwave non-absorptive, heatinsulating member, within said oven chamber, exposing said implement tomicrowave energy for a predetermined time while said microwave energyabsorptive material absorbs and so converts said microwave energy toheat energy, and transferring said heated implement to a locationexterior said oven chamber, and exposing, at said exterior location, anarticle to said stored heat as it is released from said heated microwaveabsorptive member by said heat insulating member. 6. A method of heatingan article in an oven chamber receptive to microwave energy whichincludes the steps of:

exposing to microwave energy an implement, where said implementcomprises a body which is at least partially microwave permeable andmicrowave non-absorptive enclosing a pocket of microwave energyabsorptive material, within said oven chamber for a predetermined timewhile said pocket of microwave energy absorptive material absorbs and soconverts said microwave energy to heat energy,

. and subsequently locating said article to be heated on said heatedbody thereby heating said article from said heat energy as it isreleased from said microwave absorptive material.

7. In a method of heating an article, according to claim 6, the addedstep of:

exposing said implement with said article thereupon for an additionalpredetermined time to microwave energy to heat the interior of saidarticle by said direct exposure to microwave energy and heating thesurface of said article in contact with said implement by the dualheating of both heat newly converted from said exposure to microwaveenergy within said articles surface and from heat newly converted andreleased from said pocket of microwave energy absorptive material.

8. In a method of heating an article, according to claim 6, the addedstep of:

locating a microwave non-absorptive heat insulating material in apredetermined position with respect to said pocket of microwaveabsorptive material to contain, build up and direct said heat energy,which otherwise would not reach said article, onto said article.

9. A method of heating an article in an oven chamber receptive tomicrowave energy which includes the steps of:

locating a heating implement, within said chamber,

said implement comprising:

a microwave-absorptive material,

a microwave-nonabsorptive, heating utensil, lo-

cated in contact with an obverse surface of said microwave-absorptivematerial, heated by heat released by said microwave-absorptive material,and

a heat insulator located on the reverse side of saidmicrowave-absorptive material to contain and direct heat released bysaid microwaveabsorptive material which heat would otherwise not reachsaid heating utensil, onto said heating utensil;

exposing said heating implement to microwave energy for a predeterminedtime while said microwave-absorptive material absorbs and so convertssaid microwave energy to heat energy; and

subsequently 1 locating said article on said heating utensil therebyheating said article from said heat energy as it is, in

turn, released by said heating utensil.

10. A method of heating an article, according to claim 9, where saidheating utensil is a glass-ceramic cooking utensil and said article is afoodstuff.

11. A method of heating an article in a microwave oven which comprises:

exposing a body which has a plurality of spark gap electrodes therein tomicrowave energy thereby causing an electric discharge between adjacentelectrodes and resulting in said microwave energy converting to heatenergy, and

locating said article in predetermined relationship with said dischargepath to subject said article to said heat energy and to heat saidarticle thereby. 12. In a method of heating an article, according toclaim 11, where said body comprises heat insulating material whichcontains and directs heat which otherwise would not reach said articleonto said article.

13. In a method of heating an article, according to claim 12, whichfurther includes:

locating a heat conductive element in contact with said article andbetween said article and said electric discharge whereupon said heatenergy is more equally transferred from around said electric dischargeto said article.

l II

1. A method of heating an article in an oven chamber receptive tomicrowave energy comprising: locating within said chamber a microwaveabsorptive member, locating a heat conducting member in (a preselectedrelationship) contact with said absorptive member and between saidmicrowave absorptive member and said article, and exposing saidmicrowave absorptive member to microwave energy until it absorbs and soconverts said microwave energy (into) to heat energy and said heatconducting member conducts said generated heat energy to said article.2. A method of barbecuing a foodstuff in an oven chamber receptive tomicrowave energy which comprises: locating a microwave absorptive memberwithin said oven chamber, locating said foodstuff where said microwaveabsorptive member, when heated, will be in position to heat saidfoodstuff and where at least a portion of any conbustible heat renderedby-products of said foodstuff will contact said mocrowave absorptivemember, exposing said microwave absorptive member to microwave energyuntil it absorbs and so converts said microwave energy to heat energy toa temperature at least high enough to heat render combustibleby-products from said artIcle and high enough to kindle said combustibleheat rendered by-products, and additionally heating said foodstuff bythe heat of rapid combustion of said kindled combustible heat renderedby-products.
 3. A method of heating an article in an oven chamberreceptive to microwave energy which comprises: locating a microwaveabsorptive, combustible material in said oven chamber, exposing saidmicrowave absorptive, combustible material to microwave energy until itabsorbs and so converts said microwave energy to heat energy and heatsto its ignition temperature and is set on fire, and locating saidarticle in a predetermine position where said article will be heated bythe dual heating of both the heat of combustion of said burningmicrowave absorptive, combustible material and, as it is released fromsaid material, heat converted from said microwave exposure of saidmicrowave absorptive, combustible material by said exposure of saidmaterial to microwave energy.
 4. In a method, according to claim 3, theadded step of: locating a heat conductive member in contact with saidarticle and between said article and said burning microwave absorptive,combustible material whereat to collect and conduct to said article heatenergy released by said burning microwave absorptive, combustiblematerial on said exposure to microwave energy.
 5. A method of heating animplement and storing said heat within said implement while in an ovenchamber receptive to microwave energy for subsequent use of said heatedimplement at a location external said oven chamber which comprises:locating said implement, said implement comprising a microwaveabsorptive member located within a microwave non-absorptive, heatinsulating member, within said oven chamber, exposing said implement tomicrowave energy for a predetermined time while said microwave energyabsorptive material absorbs and so converts said microwave energy toheat energy, and transferring said heated implement to a locationexterior said oven chamber, and exposing, at said exterior location, anarticle to said stored heat as it is released from said heated microwaveabsorptive member by said heat insulating member.
 6. A method of heatingan article in an oven chamber receptive to microwave energy whichincludes the steps of: exposing to microwave energy an implement, wheresaid implement comprises a body which is at least partially microwavepermeable and microwave non-absorptive enclosing a pocket of microwaveenergy absorptive material, within said oven chamber for a predeterminedtime while said pocket of microwave energy absorptive material absorbsand so converts said microwave energy to heat energy, and subsequentlylocating said article to be heated on said heated body thereby heatingsaid article from said heat energy as it is released from said microwaveabsorptive material.
 7. In a method of heating an article, according toclaim 6, the added step of: exposing said implement with said articlethereupon for an additional predetermined time to microwave energy toheat the interior of said article by said direct exposure to microwaveenergy and heating the surface of said article in contact with saidimplement by the dual heating of both heat newly converted from saidexposure to microwave energy within said article''s surface and fromheat newly converted and released from said pocket of microwave energyabsorptive material.
 8. In a method of heating an article, according toclaim 6, the added step of: locating a microwave non-absorptive heatinsulating material in a predetermined position with respect to saidpocket of microwave absorptive material to contain, build up and directsaid heat energy, which otherwise would not reach said article, ontosaid article.
 9. A method of heating an article in an oven chamberreceptive to microwave energy which includes the steps of: locating aheating implement, within said chamber, said implement comprising: amicrowave-absorptive material, a microwave-nonabsorptive, heatingutensil, located in contact with an obverse surface of saidmicrowave-absorptive material, heated by heat released by saidmicrowave-absorptive material, and a heat insulator located on thereverse side of said microwave-absorptive material to contain and directheat released by said microwave-absorptive material which heat wouldotherwise not reach said heating utensil, onto said heating utensil;exposing said heating implement to microwave energy for a predeterminedtime while said microwave-absorptive material absorbs and so convertssaid microwave energy to heat energy; and subsequently locating saidarticle on said heating utensil thereby heating said article from saidheat energy as it is, in turn, released by said heating utensil.
 10. Amethod of heating an article, according to claim 9, where said heatingutensil is a glass-ceramic cooking utensil and said article is afoodstuff.
 11. A method of heating an article in a microwave oven whichcomprises: exposing a body which has a plurality of spark gap electrodestherein to microwave energy thereby causing an electric dischargebetween adjacent electrodes and resulting in said microwave energyconverting to heat energy, and locating said article in predeterminedrelationship with said discharge path to subject said article to saidheat energy and to heat said article thereby.
 12. In a method of heatingan article, according to claim 11, where said body comprises heatinsulating material which contains and directs heat which otherwisewould not reach said article onto said article.
 13. In a method ofheating an article, according to claim 12, which further includes:locating a heat conductive element in contact with said article andbetween said article and said electric discharge whereupon said heatenergy is more equally transferred from around said electric dischargeto said article.